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RFC 1700 - ip-parameters

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    IP OPTION NUMBERS

    The Internet Protocol (IP) has provision for optional header fields
    identified by an option type field.  Options 0 and 1 are exactly one
    octet which is their type field.  All other options have their one
    octet type field, followed by a one octet length field, followed by
    length-2 octets of option data.  The option type field is sub-divided
    into a one bit copied flag, a two bit class field, and a five bit
    option number.  These taken together form an eight bit value for the
    option type field.  IP options are commonly refered to by this value.

    Copy Class Number Value Name				Reference
    ---- ----- ------ ----- ------------------------------- ---------
       0     0      0     0 EOOL   - End of Options List    [RFC791,JBP]
       0     0      1     1 NOP    - No Operation           [RFC791,JBP]
       1     0      2   130 SEC    - Security                  [RFC1108]
       1     0      3   131 LSR    - Loose Source Route     [RFC791,JBP]
       0     2      4    68 TS     - Time Stamp             [RFC791,JBP]
       1     0      5   133 E-SEC  - Extended Security         [RFC1108]
       1     0      6   134 CIPSO  - Commercial Security           [???]
       0     0      7     7 RR     - Record Route           [RFC791,JBP]
       1     0      8   136 SID    - Stream ID              [RFC791,JBP]
       1     0      9   137 SSR    - Strict Source Route    [RFC791,JBP]
       0     0     10    10 ZSU    - Experimental Measurement      [ZSu]
       0     0     11    11 MTUP   - MTU Probe                 [RFC1191]
       0     0     12    12 MTUR   - MTU Reply                 [RFC1191]
       1     2     13   205 FINN   - Experimental Flow Control    [Finn]
       1     0     14   142 VISA   - Expermental Access Control [Estrin]
       0     0     15    15 ENCODE - ???                      [VerSteeg]
       1     0     16   144 IMITD  - IMI Traffic Descriptor        [Lee]
       1     0     17   145 EIP    - ???			   [RFC1358]
       0     2     18    82 TR     - Traceroute		   [RFC1393]
       1     0     19   147 ADDEXT - Address Extension    [Ullmann IPv7]
       1     0     20   148 RTRALT - Router Alert                 [Katz]
       1     0     21   149 SDB    - Selective Directed Broadcast[Graff]
       1     0     22   150 NSAPA  - NSAP Addresses          [Carpenter]

    IP TIME TO LIVE PARAMETER

    The current recommended default time to live (TTL) for the Internet
    Protocol (IP) is 64 [RFC791, RFC1122].

    IP TOS PARAMETERS

    This documents the default Type-of-Service values that are currently
    recommended for the most important Internet protocols.

    TOS Value	Description				Reference
    ---------	--------------------------		---------
      0000		Default					[RFC1349]
      0001		Minimize Monetary Cost			[RFC1349]
      0010		Maximize Reliability			[RFC1349]
      0100		Maximize Throughput			[RFC1349]
      1000		Minimize Delay				[RFC1349]
      1111		Maximize Security			[RFC1455]

    The TOS value is used to indicate "better".  Only one TOS value or
    property can be requested in any one IP datagram.

    Generally, protocols which are involved in direct interaction with a
    human should select low delay, while data transfers which may involve
    large blocks of data are need high throughput.  Finally, high reliability
    is most important for datagram-based Internet management functions.

    Application protocols not included in these tables should be able to
    make appropriate choice of low delay (8 decimal, 1000 binary) or high
    throughput (4 decimal, 0100 binary).

    The following are recommended values for TOS:

                ----- Type-of-Service Value -----

    Protocol           TOS Value

    TELNET (1)         1000                 (minimize delay)

    FTP
      Control          1000                 (minimize delay)
      Data (2)         0100                 (maximize throughput)

    TFTP               1000                 (minimize delay)

    SMTP (3)
      Command phase    1000                 (minimize delay)
      DATA phase       0100                 (maximize throughput)

    Domain Name Service
      UDP Query        1000                 (minimize delay)
      TCP Query        0000
      Zone Transfer    0100                 (maximize throughput)

    NNTP               0001                 (minimize monetary cost)

    ICMP
      Errors           0000
      Requests         0000 (4)
      Responses         (4)

    Any IGP            0010                 (maximize reliability)

    EGP                0000

    SNMP               0010                 (maximize reliability)

    BOOTP              0000

    Notes:

    (1) Includes all interactive user protocols (e.g., rlogin).

    (2) Includes all bulk data transfer protocols (e.g., rcp).

    (3) If the implementation does not support changing the TOS
    during the lifetime of the connection, then the
    recommended TOS on opening the connection is the default
    TOS (0000).

    (4) Although ICMP request messages are normally sent with
    the default TOS, there are sometimes good reasons why they
    would be sent with some other TOS value.  An ICMP
    response always uses the same TOS value as was used in the
    corresponding ICMP request message.

    An application may (at the request of the user) substitute
    0001 (minimize monetary cost) for any of the above values.

    REFERENCES

    [RFC791] Postel, J., "Internet Protocol - DARPA Internet Program
             Protocol Specification", STD 5, RFC 791, DARPA, September
             1981.

    [RFC1108] Kent, S., "U.S. Department of Defense Security Options for
              the Internet Protocol", RFC 1108, BBN Communications,
              November 1991.

    [RFC1122] R. Braden, Ed., "Requirements for Internet Hosts --
              Communication Layers," IETF Host Requirements Working Group,
              RFC-1122, October 1989.

    [RFC1191] Mogul, J., and S. Deering, "Path MTU Discovery", RFC 1191,
              DECWRL, Stanford University, November 1990.

    [RFC1349] Almquist, P., "Type of Service in the Internet Protocol
              Suite", RFC 1349, Consultant, July 1992.

    [RFC1358] Chapin, L., Chair, "Charter of the Internet Architecture
              Board (IAB)", RFC 1358, Internet Architecture Board, August
              1992.

    [RFC1393] Malkin, G., "Traceroute Using an IP Option", RFC 1393,
              Xylogics, Inc., January 1993.

    [RFC1455] Eastlake, D., "Physical Link Security Type of Service",
              RFC 1455, Digital Equipment Corporation, May 1993.

    [Ullmann IPv7]

    PEOPLE

    [Carpenter] Brian Carpenter, , June 1995.

    [Estrin] Deborah Estrin  October 1994.

    [Finn] Greg Finn  October 1994.

    [Graff] Charles "Bud" Graff, , March 1995.

    [Katz] Dave Katz  November 1994.

    [JBP] Jon Postel  October 1994.

    [Ullmann] Robert Ullmann

    []

Connected: An Internet Encyclopedia
RFC 1700 - ip-parameters